Electric braking.



1. F. TRITLE.

ELECTRIC BRAKING. APPLIOA'HOK 11.11: In 2, 1010'.

Patented-0t.-25, 1910.

'2 SHEETS-SKEBTI.

Witnesses: Y Inventor: 5M 5 /cf&/, John Ff Tr'itle,

His fl ttor'neg.

J. F. TRITLEI ELECTRIC BRAKING. nruuumu FILED run, 1910.

973,590, I Patented Oct. 25, 1910.

2 SHEETS-QHEET 2.

Witnesses: I Inventor:

\ 1 Hisflttorheg.

citizen of the United States, residin UNITED STATES PATENT. oFFIoE.

JOHN ll. TBI'LLE, OF SGHENECTADY, NEW YORK, ASSIGNOR '20 GENERAL MPAIN'Y, A CORPORATION OF NEW YORK."

nnnc'rnrc nnaxme.

Specification of Letters Patent. I

Patented Oct. 25,1910.

Application meam 2,1910. Serial m. 588,925.

To all whom it may concern:

Be it known thatI, JOHN F. Turrnn, a

Schenectady, county of Schenectady, t'ate of New York, have invented certain new and useful Improvements in Electric Braking, of which the following is a specification.

My invention relates to the control of electric motors to cause them to act as braking generators for returning current to the hue or to the source,- and its object is to procompounding the the first exciter.

vide means for compensating, to some extent, for variation in the motor speed so as to maintain an efi'ective braking action as the motor speed falls. I accomplish" this result by roviding means for separately exciting tlie motor fields and automatlcally excitation to compensate for varying motor speed. More speclfically, I provide a separate exciter with a second exciter varyin in speed with the motor and exerting a di erent al action on the field of My invention will best be reference to the accompanying drawing in which- I Figure 1 shows diagrammatically a pair of direct current motors provided with controlling means arranged 1n accordance with my invention; and Figs. 2 and 3 show diagrammatically my invention applied to the control of alternating current motors.

In Fig. 1, A A represent the armatures of a pair of direct current motors and B B their fields. The motor armatures are shown exciter,

connected through the resistance 0 to a source of current or tea trolley wire through the trolley D. E represents the the exciter for these motors. This exciter may be driven at constant speed or from the motor'axlesj It has a main field F excited from the source througha resistance G and a 'difierential fieldH excited from the armature I of a second exciter which is driven from the car axle so as to vary in speed with the motors A A The field of this second indicated at J, is excited. from the source and may be connected in series with 0 the main field F of the exciter understood by.

speed, it is-poss-ible by I quantities large, relatively to their difierarinature of acting as braking generators it will be seen that as the motor s eed falls the braking act1on will tend to iminishbecause ofdecreased induced voltage in the motor armatures, but a decrease in speed in the motors means a decrease in speed in the exciter armature I, the voltage of which corres ondingly decreases. This weakens the differential effect in the field winding Hand increases the voltage per revolution of the exciterE. This exciter, therefore, furnishes more current to the field windings B B and thereby compensates to a greater or less extent for the drop in voltage/of the motors. Thus the excitation of the motors is automatically compounded-by the varying differential effect of the exciter I on the field of the exciter' E, Ad ustment for diiferent speeds and braking e sets may be-obtained by adjustingthe amount of resistance C or of resistance G as is indicated diagrammaticallv in the drawing.

It theexciter armature E is driven at con-' stant speed,

its voltage obviously will rise as the-speed ofthe motor armatures A A and therefore of armature I falls, so that by proper adjustment of windings F- and H the voltage of armatures A A? maybe'held practically constant over a wide range of s eed. If the armature E is driven from t e axle, the voltage of armatures A A cannot be held so nearly constant, but since the field that induces the voltage in the armature E is the difierence of two quantities, one constant and one varyingwith the ence, to produce a much greater percentage variation in their difference than 111" the quantity whlch varies. In other words, the

resultant of fields F and H may. increase:

considerably faster. than the speed of armature E decreases, over a certain range-so that over that range the strengths of fields B and B may be increased as the speed of armatures A A falls so as to maintain the armature voltage of the motors and consequently their braking eilect.

The arrangement shown in Fig. 1 cannot be applied precisely in that form to alternating current motors since the phase relamaking those two tions of the several circuits would not be correct For instance while the voltage impressed upon the field winding E would be in phase with the voltage of the source, the

voltage impressed upon the field winding H would be in phase with the voltage of armature I which isin phase with the current in field winding J and consequently approximately in uadrature with the voltage of the source. bus the magnetizing efi'ects of the two windings F and H would be in 2.5-'- r't i ary of this winding is connected to the quadrature and not in o'p'positionl' The same principle, however, is applicable toalternating current motors and may be embodied in several different arrangements.

'One such arrangement; is shown in Fig. 2.

In thisfigure the motor armatu'res-A andA are shown connegt-ed to the transformer winding K which in this; case acts as a source of current for the-motors. The 'field windings Band B are excited from the armature E of an exciter which in this case has only a singile field-winding F supplied from the secon ary of the: transformer L. The prisource but has in series with it the armature I'of the second exciter, the field winding J of thlcSiGXCitBI being so connected as tocause the voltage of the armature I to oppose the voltage of the source in the circuit of the primary. of transformer L.

The as-has een described for Fig. 1. As the speed-decreases, the voltage of armature I decreases, thereby weakening its differential eflect and causing-the resulting voltage of the primary of transformer L to rise.

' ,sating windings for theniotors, suchwind- I motors. I

This-increases theffield excitation in. winding F and therefore the voltage per revolutionof'exciter armature E. The field J in this case is shown connected in series with the motor fields B and B and thererore excited from the exciter- The connections shown in this figure give proper phase relations in the several circuits. It-will-be understood that-while for the sake of simplifying the diagram 1 have shownno compenings "would in practicebe employed as is' customary in alternat ng current' series .In-Fig. 3 the same arrangement is shown as inllFig'- 2" except that the field'J of thesecond exciter' is placed in series with the motoparmatur'e's' instead of the motor fields.

In thisicase not onl does the drop in -speed of the excitei' I re me its voltage also it the current returned by the motors-tethe line is, jduced, the strength"of"fi'eldwind ofarmatur'e I further weakened;

Further modifications of my invention both for-direct'and alternating current ino- J -.is decreas d thereby and the voltage tors will be obvious to those sk ill ed in the rinciple. of operation is thesame.

mected tothe field winding a transformer having its. pr mary connectedto the source and its secondary to ",former and its fiel predfuce an armature =voltage ,opposmtg the art. Accordingly I do not desireto limit myself to the particular connections and arrangement of parts shown and described but a1m 1n the ap ended claims to cover all modifications w rich are within the scope of my mvention.

hat I claim asnew and desire to secure by Letters Patent of the United States, is,--

1. In combination with an electric motor and a source of current therefor, means for causing the motor to act as a braking generator for returning energy to the source, consisting of means for separately exciting the field winding of the motor, and means 'for automatically compounding'th excita-. tion'to compensate for'varying speeds.

2. Ijn'conibination' with an electric motor and a source of current therefor, means for causing the motor to act as a braking gen erator for returning energy tofthe source, sald means consisting of a separate excit'er for exciting the field winding of the motor,

and means for automatically varying the voltage per revolution of the exciter to compensate for variation in themo'torjspeed.

3. In combinationwith an electric motor and a source/of cur'renttherefor, means for causing the motor to act as a braking generator to return energy to the source com- 1 prising an exciter for separately exciting the motor field and a second exciter varying in speed with the .motor and having its armature connected to exert a difi'erential' effect upon the field of the first mentioned exciter so as to increase the-voltage per revolution of the first mentioned exciter as the motor speed decreases. 4. In combination with an electric motor and a source of current therefor, means for causing the motor to act as a braking generator to return energy to the line, consisting'of an exciter for separately exciting the motor field and a second exciter varying in speed with the motor, the field of the first- "mentionedexciter being excited differentially by voltage derived from the source and from the armature of the second exciter.

5. In combination with an alternating ing the motor to act as a braking generator "for returning energy to the source, consist-' ainglof an exoiter having its armature conthe field winding of said exciter', and a of the motor and v iseccnd exciter' having its armature connected rimar of said transwinding connected to in series with the Volta e of the source in the circuit 0 aid trans ormer primary 6. In combination wlth an electric motor enator for returning energy to the source, In Witness w ereof, I

Ind a source of current therefor, means ior field of the motor so as to compensate for causingthe motor to act as a bra-king genvarying motor 5 eed. 10

have hereunto set consisting of an exclter for separately exeitmy'hand this 30th da of April, 1910.

ing the motor field and a second exciter OHN F. TRITLE. varying in speed with the motor and having Witnesses: its armature connected to produce a difi'eren- BENJAMIN B. HULL, tial efl'eot proportional to its voltage on the HELEN .ORFORD. 

